High efficiency process for treating mixed metal waste

ABSTRACT

A process for rendering hazardous materials present in multi-element waste non-hazardous, and for recovering valuable components of said waste, particularly metals, comprising contacting the waste with an aqueous solution of HX, wherein X is halogen, thereby converting metals present in the waste to the corresponding halides, and subsequently separating said metal halides from other components of the reaction mixture and from each other.

FIELD OF THE INVENTION

The present invention is concerned with the treatment of mixed metalwaste. More specifically, the present invention relates to a process forseparating and recovering metals from mixed waste by means of convertingsaid metals to the corresponding halides, and to apparatus for carryingout said process.

BACKGROUND OF THE INVENTION

The large-scale production of waste materials, primarily inindustrialized countries, has led to major ecological and economicproblems on a worldwide scale. Waste materials, which may be defined asundesired substances that result from the production or use of adesirable, useful material, are of three main types: household,industrial and toxic or hazardous waste.

In the absence of efficient waste recycling plants, very large amountsof waste materials are deposited in landfill sites, which entails highcost, both to the environment and to the economy. In addition to theproblems arising from pollution, fire and explosion risk, an additionalconcern is the loss of potentially valuable raw materials which couldotherwise be recycled for use as starting materials or intermediates formany manufacturing processes.

While many different recycling technologies have been developed, theseare generally applicable only to single materials or a class ofmaterials, and hence require sorting or pre-processing of the waste.

The problem is compounded when the waste material includes highly toxic,inflammable, and potentially explosive substances. The increasinglywidespread use, and hence disposal, of electrical batteries provides anexample of the generation of toxic waste from industrial and householdsources. Electrical batteries are a source of chemical contamination, asa result of their toxic components such as cadmium, cobalt and nickel.In addition, they may pose a fire hazard and explosion risk as aconsequence of components such as Lithium and other exothermicmaterials.

U.S. Pat. No. 4,637,928 discloses a method for treating articles such asbatteries by opening the battery casings and contacting the interiors ofsaid batteries with an alkaline agent.

Co-owned International patent application no. PCT/IL99/00045,incorporated herein by reference, discloses a recovery process for mixedwaste, in which components such as metals are separated from each otheras halides, following gaseous phase halogenation. Although this processis highly efficient, for certain applications the equipment required maybe relatively expensive.

It is a purpose of the present invention to provide a highly efficientprocess for the recovery of metals from unsorted mixed waste, inparticular from electrical batteries. It is a further purpose of thepresent invention to convert hazardous components present in the wasteto non-hazardous materials.

It is another object of the present invention to provide a process thatis ecologically clean, economically advantageous and industriallyconvenient.

It is a further object of the present invention to provide a process forrendering electrical batteries non-hazardous, while also permittingrecovery of the valuable raw materials contained therein.

Other objects and advantages of the invention will become apparent asthe description proceeds.

SUMMARY OF THE INVENTION

It has now been found that it is possible to render hazardousmixed-waste materials non-hazardous by virtue of their contact with anaqueous solution of HX, wherein X is a halogen, and to recover certainvaluable components, particularly metals, from said waste. Recovery ofthe metallic components is achieved by virtue of their conversion to thecorresponding halides, said metal halides being subsequently separatedfrom the reaction mixture and from each other. Thus, the aqueous HXsolution serves two distinct purposes: firstly, to provide a medium inwhich hazardous material can be rendered non-hazardous, and secondly, topermit the recovery of valuable metals therefrom in the form of halides.

Thus, the present invention provides a high efficiency process forrendering hazardous materials present in multi-element waste nonhazardous, and for recovering valuable components of said waste,particularly metals, comprising contacting the waste with an aqueoussolution of HX, wherein X is halogen, thereby converting metals presentin the waste to the corresponding halides, and subsequently separatingsaid metal halides from other components of the reaction mixture andfrom each other.

According to a preferred embodiment of the present invention, the wasteto be treated comprises electrical batteries, such as lithium or nickelbatteries. In another embodiment, the waste comprises electricalequipment or electrical devices, e.g., cellular telephones, which mayoptionally be treated according to the invention together with thebatteries contained therein.

A major advantage associated with the application of the presentinvention to the treatment of lithium batteries is that the processinvolves a reaction between the components of the batteries and anaqueous solution of HX, namely, a reaction in the liquid phase. Thispermits hazardous compressed gases such as SO₂ or SOCl₂, that arepresent in said batteries as the electrolytic medium, to be absorbed bythe aqueous solution. In addition, according to the present invention,hazardous lithium metal is converted in the solution to LiX.

In a preferred embodiment of the invention, oxidising agents are presentin the aqueous solution of HX, to enhance the oxidation power of thesolution. Preferably, the oxidising agent is hydrogen peroxide, theconcentration of which in the solution is between 0.1 and 5% (w/w).

The term “the reaction” is used hereinafter to refer to the conversionof the metals present in the waste to the corresponding halides, by thereaction of said metals with HX, wherein X is a halogen, or optionallyby the reaction of said metals with the above mentioned oxidisingagents. In a preferred embodiment, the reaction is carried out at atemperature of between 20 and 90° C., and more preferably, at atemperature of between 50 and 80° C.

In a preferred embodiment of the invention, the aqueous solutioncontaining HX is HCl solution or HBr solution, HCl solution being mostpreferred. The concentration of the solution is between 5 and 33% (w/w),more preferably between 15 and 25% (w/w). In another preferredembodiment, an aqueous solution containing a combination of HCl and HBris used in the reaction. A preferred combination is provided by asolution of HCl, comprising between 1 and 10% (w/w) HBr.

Preferably, the reaction is performed with agitation. Preferred modes ofagitation are selected from the group of mixing, vibrating, shredding,liquid circulation, and forced gaseous/air turbulent mixture aeration.

Preferably, the waste material is brought into contact with the aqueoussolution of HX at a controlled rate, to allow controlled evolution ofthe gaseous H₂ formed in the reaction. This gas is preferably removedfrom the reaction mixture, together with other gases that are notdissolved by the reaction mixture, or which are only partially dissolvedthereby, and are optionally recovered. Preferably, the reaction iscarried out under reduced pressure in order to facilitate the removal ofsaid gases.

The waste material may also contain various gases that are soluble inthe aqueous reaction medium, for example, SO₂ and SOCl₂, as found inlithium batteries. These gases are rendered non-hazardous by virtue oftheir becoming absorbed by the aqueous medium. In addition, thedissolved gases increase the acidity of the solution, and thehalide-containing gases such as SOCl₂ act as a halide source for thereaction solution.

The separation of the metal halides from the reaction mixture and theirsubsequent separation from each other are accomplished by methods knownin the art. Most of the metal halides formed in accordance with thepresent invention are water soluble, and therefore, in order to separatesaid halides from the reaction mixture, known liquid/solid separationtechniques may be employed, such as, for example, filtration. Thus, in apreferred embodiment of the present invention, the reaction mixture isfiltered to obtain a filtrate containing said soluble halides.Typically, the filter cake consists of plastics and carbon materialsthat were initially present in the raw waste, and did not undergochemical reaction. The filter cake may also contain insoluble metaloxides, which may be recovered, if desired, by treating said cake with abase.

In a preferred embodiment of the present invention, the metals arerecovered from the filtrate by causing the selective precipitation ofsome of the metals. Optionally, metal recovery may also be achieved byusing ion exchange or selective extraction. Preferably, the selectiveprecipitation is carried out by treating the filtrate with an alkalineagent, preferably NaOH, to allow the separation between water solublehydroxides, particularly, LiOH, from water insoluble hydroxides, such asFe(OH)₃, Ni(OH)₂, Cd(OH)₂, Co(OH)₂ and Al(OH)₃. Subsequently, the nonsoluble hydroxides are separated from the liquid phase, preferably byfiltration, and the filtrate, containing Li⁺ (and Na⁺), is furthertreated to cause the selective precipitation of lithium, preferably inthe form of LiF or LiCO₃, generally by introducing into said filtrateNa₂CO₃ or NaF. The water insoluble lithium salt may be separated byfiltration, and the filtrate obtained is preferably evaporated torecover NaCl therefrom. The insoluble hydroxides are separable bymethods known in the art.

According to the present invention, metals, the halides of which arewater insoluble, may also be present in the mixed waste. These metalsmay be recovered from the solid phase of the reaction mixture bystandard methods.

Optionally, the reaction according to the present invention is precededby heat treatment of the raw waste material and/or mechanical processingof said waste material. In one embodiment, the heat treatment isperformed prior to said mechanical processing. In a second embodiment,the waste material is subjected to simultaneous heat treatment andmechanical processing. The mechanical processing is intended totransform the waste into a particulate form, to facilitate the reaction.In one embodiment, the reaction is carried out concurrently with saidprocessing.

The optional heat treatment stage is performed under conditions allowingthe removal from the waste of gases or liquids, particularly water, andorganic material, which typically constitute part of the raw wastematerial, preferably by evaporation in the case of water, andevaporation or carbonization in case of organic matter. The heattreatment is performed in a controlled oxygen atmosphere preferably at atemperature of less than 1000° C. Alternatively, the heat treatment maybe performed in a metallic molten bath, said bath preferably being at atemperature of between 500° C. and 1600° C. According to anotherembodiment, the heat treatment is pyrolysis.

The optional mechanical processing of the waste, prior to the reactionwith an aqueous solution of HX according to the present invention, isintended to remove the coating from the metal parts and to reduce thewaste particle size, in order to provide small metallic particles whichmay easily react with said HX, thus facilitating both rapid reactiontimes and also easier handling of the partially processed wastematerial. The mechanical processing preferably comprises one or more ofthe following operations: mechanical shaping of solid waste into unitsof a size and shape appropriate for subsequent processing;

shredding, scraping, crushing and/or milling;

briquetting of sludge.

Preferably, the mechanical processing comprises shredding the wastematerial in a controlled environment. In a preferred embodiment, thecontrolled environment is provided by a gas such nitrogen or a noblegas, e.g., argon, or a liquid.

In another preferred embodiment of the present invention, said heattreatment and/or said mechanical processing are carried out in eitherorder, subsequent to the reaction. In another embodiment, the mechanicalprocessing and the reaction are carried out concurrently.

In another aspect, the invention is directed to an apparatus forrendering hazardous materials present in multi-element wastenon-hazardous, and for recovering valuable components of said waste,comprising:

a reaction chamber, for reacting multi-element waste with a solution ofHX, wherein X is a halogen;

means for introducing said waste into said reaction chamber at acontrolled rate;

means for removing gaseous products from the reaction chamber;

means for discharging the metal halide products from the reactionchamber and means for separating said metal halides from each other.

According to a preferred embodiment, the apparatus further comprises aheating chamber comprising means of heating, a waste inlet and an outletleading from said heating chamber to the reaction chamber. According toone preferred embodiment of the invention, the apparatus furthercomprises means for the mechanical processing of the waste material,which means is preferably a shredder, located between said outlet of theheating chamber and the inlet of the reaction chamber. Alternatively,the shredder may be positioned at the inlet of said heating chamber.According to another embodiment, the shredder is located within theheating chamber or in the reaction chamber.

The reaction chamber is preferably equipped with heating/cooling meansand with agitation means.

Preferably, the means for introducing raw waste material into saidreaction chamber at a controlled rate comprises a conveying system suchas a conveyor belt, which transports the waste to the reaction chamber.In one preferred embodiment, the conveyor belt is fully enclosed in aprotected atmosphere, provided by a gas such as nitrogen or argon thatwill not react with the hazardous components which may be part of theraw waste. When the apparatus according to the present inventioncomprises a shredder, the shredding rate is controlled to allow thewaste material to be discharged therefrom, and to be fed into thereaction chamber, at a desired rate.

Preferably, the means for removing gaseous products from the reactionchamber comprises a scrubbing system.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more clearly understood from the detaileddescription of the preferred embodiments and from the attached drawingsin which:

FIG. 1 is a schematic diagram of one embodiment of an apparatus forperforming high efficiency treatment of mixed metal-containing wastes.

FIG. 2 is a schematic diagram of a further embodiment of an apparatusfor performing high efficiency treatment of mixed metal-containingwastes.

FIG. 3 is a flow chart of one embodiment of the process according to thepresent invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

According to one embodiment of the present invention, which will bedescribed with reference to FIG. 1, the waste to be treated is insertedinto a hopper 1, which is maintained at a controlled atmosphere,provided by a gas such as nitrogen or argon, and is further providedwith a means for controlling the rate of discharge of the wastetherefrom. Controlled, predetermined amounts of waste pass through agate, 1 a, to enter the heating chamber, 2. Heating chamber, 2, which ismaintained at a controlled atmosphere, preferably rotates on wheels, 2a, and is heated by external heating elements, 2 b, or by a burner in acontrolled atmosphere. The concentrations of oxygen and/or gaseouscomponents in the heating chamber are regulated by the gate valves, 1 a.The amount of waste being transported through the chamber is regulatedby the rotating speed of the chamber or by other transporting means suchas a walking beam or conveyor belt. The waste falls by gravity into theshredding chamber, 3, which comprises known components such as jawcrushers, rotating shredding knives, etc. The size of the shreddedparticles vary according to the type of waste material, speed ofoperation and so forth. The shredder operates within a protectedatmosphere, in which the levels of water and other liquid and gaseouscomponents are controlled. The shredding rate is adjusted according tothe rate of reaction in the reaction chamber, 4, and in particular,according to the rate of gas generation and/or removal. The reactionchamber, 4, is made of a material that will withstand a chemicalreaction between metals and HX solutions at temperatures up to 140° C.,such as various common polymers, for example, polyamide or PVDF. Saidreaction chamber is fitted with inlets/outlets, 4 a, for theintroduction of various chemicals in liquid form for the reaction andalso for circulating the solution through an externally placed heatexchanger. In a preferred embodiment a solution of 15–30% HCl, 0.1–1%H₂O₂, 0.05–10% HBr and 0–10% sulfuric acid is used for the reaction withbatteries. The reaction chamber may also be fitted with a heating orcooling jacket, 4 b, where a liquid, 6, may be introduced from anotherexternal source. Other heating elements (for example electricalelements) can also be incorporated into the design of the reactionchamber. A mixing device, 5, is used to mix the solution and theshredded material in order to improve the reaction between the wastematerial and the HX solution. The mixing speed may be adjusted accordingto the type of reaction mixture, particle size, and other chemical andphysical parameters. In another preferred embodiment, air is injectedinto the lower region of the reactor in order to assist in mixing theparticles and to add oxygen to the reaction. The gases that evolveduring the course of the reaction, and also the gases which were alreadypresent in the waste material, such as SO₂, will be absorbed by thesolution of the reactor, or will react with said solution. Thenon-dissolved gases will then be bubbled upwards to be collected in thescrubbing system, 13, through the fan blower system, 14. The undissolvedmaterials, mainly plastics are discharged through a conduit, 11, at thelower end of the reaction chamber, 4, passing through liquid filterapparatus, 7, to be discharged to solid waste chamber 8. The liquidphase containing the metal chlorides is delivered, by means of pump, 7a, through valves 12 to various means, 9 and 10, for separating themetal halides, said means being based on known technologies such asselective precipitation, extraction, absorption and ion exchange. Theseparating means 9, and 10 also remove contaminants from the metalhalides, thus permitting further processing of said metal halides intocommercially-useful compositions.

According to a preferred embodiment of the present invention, the scrapwaste to be treated comprises lithium batteries having compressed SO₂and/or SOCl₂ as an electrolyte, or electrical equipment comprising suchbatteries. The batteries may still be partly or fully charged, andcontain lithium metal which may easily ignite and explode if exposed towater and air, producing hydrogen gas. The process of the presentinvention will render the batteries non-hazardous, while also permittingrecovery of the valuable raw materials contained therein. The embodimentof the present invention related to the recovery of valuable metals fromelectrical equipment and/or batteries will be described with referenceto FIG. 2.

The batteries, which are encapsulated in plastic film, but which havetheir metal leads exposed, are fed at a predetermined rate by aconveying system, 2 d, which comprises a conveyor belt which,optionally, may be enclosed in a protected atmosphere, into the reactionchamber, 4. The rate of introduction of the batteries is partlydetermined by safety considerations (for example, as a function of theenergy produced, efficiency of the venting system, hydrogen productionand the maximum permissible temperature in the reaction chamber).

The reaction chamber 4 contains a 30% HCl water solution at 50° C.supplemented with 5% H₂O₂. The battery lead face, which is an ironalloy, will react with the chloride solution to emit H₂, which is ventedthrough the scrubber. The venting system is designed so that the flow ofair and the possible H₂ production will always be at a level below thecritical level for explosions to occur. Generally, H₂ concentration maynot be permitted to exceed 2% of the total gas volume present in thereaction chamber, at any time.

The chloride solution causes pitting of the battery's metal casing, andeventually will produce tiny holes. The SO₂ gas and/or the SOCl₂ gascontained within the batteries will be released therefrom, as evidencedby bubbling. Due to the small size of the holes the bubbles will becorrespondingly small with a very large surface area. These bubbles willmix well with the hot solution and will react to form sulfuric acid.

A battery that is fully charged will be short-circuited as soon as itcontacts the solution. This may, in fact, increase the rate of reactionwithin the battery, the compressed SO₂ escaping from the batteryexplosion valve. The effect will be accommodated in the reaction chamberbecause of its size and also since the battery will be beneath thesurface of the solution. Gaseous SO₂ will react with the water and onlytraces will be emitted to the surface to be vented to the scrubber (13)further to be absorbed by caustic soda. Once the compressed gas hasescaped from the battery, its toxicity and hazard level is greatlyreduced. The solution will seep into the battery to react slowly withthe Lithium metal to produce LiCl. The reaction is exothermic butbecause of the slow rate of introduction of the solution through thetiny holes, the temperature level can be controlled. Furthermore, atfast reaction rates, there may be hot spots that may lead to anexplosive effect. During the process the metal components will reactwith the solution to produce metal chlorides such as FeCl₃, NiCl₂, LiCl,and CuCl₂ while the plastic parts will remain largely unreacted. The SO₂absorbed in the solution will add to the acidity and may produce othersalts such as CuSO₄ and FeSO₄.

The metal halides formed in the solution are pumped either directly fromthe reaction chamber, 4 a, or following shredding and/or filtration, tobe further treated and separated in separation modules 9 and 10, byknown hydrometallurgy techniques. The shredder, 3, and the heatingchamber, 2, are both optional, and in one preferred embodiment arelocated after the liquid/solid filter, 7, such that the solid materialthat does not pass through said filter is passed on to the shredder, 3.The shredded material leaving shredder, 3, passes into the heatingchamber, 2. Residual solids are collected in the optional solids tank,8, while the gaseous products of the heat treatment are removed viascrubbers, 13, clean air being evacuated by fans, 14.

The unreacted components, mainly plastics, are removed, washed to removeany chloride and further processed either by incineration, land fill orby a known plastic recovery system. In a preferred embodiment theplastic parts are incinerated in order to produce steam for use by theplant.

FIG. 3 is a flow chart illustrating the process of the present inventionand the recovery of the metals present in electrical batteries employingseparation methods based on selective precipitation.

EXAMPLE 1

A single lithium ‘D’ battery weighing 85 grams, containing 4 g lithium,was placed in 300 mL of a 20% (w/w) solution of aqueous HCl for a periodof 90 minutes. The reaction, as evidenced by the appearance of bubbling,began after 7 minutes. The temperature of the solution increased from aninitial 21° C. (ambient temperature) to 50° C. after 48 minutes. Themaximum temperature reached during the course of the reaction was 65° C.The color of the solution started to become yellow after 11 minutes, dueto the absorption of oxides of sulfur by the solution. No explosiveevents were recorded. Following the reaction, the solution was filtered,and the filtrate was found to contain 3.3 g of lithium. The lithium wasrecovered from the reaction solution as follows:

Sodium hydroxide was added to the halide solution until a pH of 4–5 wasreached, in order to permit precipitation of the hydroxides of most ofthe metals with the exception of lithium. This mixture was then filteredin order to achieve separation of the solid and liquid phases, thelatter containing lithium hydroxide. Sodium carbonate was added to theliquid phase until, at a pH of about 8, a precipitate of lithiumcarbonate was obtained. This precipitate was then filtered yieldingtechnical grade lithium carbonate, weighing 16 g.

While specific embodiments of the invention have been described for thepurpose of illustration, it will be understood that the invention may becarried out in practice by skilled persons with many modifications,variations and adaptations, without departing from its spirit orexceeding the scope of the claims.

1. A process for recovering metals from electrical batteries havingmetal casings and for rendering hazardous materials present thereinnon-hazardous, wherein said process comprises the steps of: a) placingthe electrical batteries while still enclosed in their metal casings inan aqueous solution of HX, wherein X is chlorine or bromine, andmechanically agitating said electrical batteries to form an aqueousreaction mixture into which gases released from said electricalbatteries are absorbed; b) ventilating hydrogen gas emitted from thesolution; c) filtering said reaction mixture to form a solid residualwaste and a first filtrate containing water-soluble metal halides formedfrom the reaction of HX and the electrical batteries; and d) recoveringmetals from said metal halides.
 2. A process according to claim 1,wherein the mechanical agitation of step (a) comprises shredding theelectrical batteries.
 3. A process according to claim 2, wherein theelectrical batteries are lithium batteries comprising sulfur containinggases, wherein said gases are released from said batteries to becomeabsorbed by the aqueous solution.
 4. A process according to claim 3,wherein the metals are recovered by the following steps: treating thefirst filtrate containing the metal halides with an alkaline agent, toprecipitate water-insoluble metal hydroxides in said first filtrate;separating said metal hydroxides from the liquid phase to obtain solidmetal hydroxides and a second filtrate; and isolating lithium from saidsecond filtrate.
 5. The process according to claim 2, wherein thesolution of HX is a solution of HCl having a concentration in the rangeof 5 to 33 wt %.
 6. The process according to claim 5, wherein the HClsolution further comprises from 1 to 10 wt % of HBr.
 7. The processaccording to claim 2, wherein the aqueous solution of HX furthercomprises an oxidizing agent.
 8. The process according to claim 7,wherein the oxidizing agent is H₂O₂.
 9. The process according to claim4, wherein the solid metal hydroxides comprise one or more of thefollowing salts: Fe(OH)₃, Ni(OH)₂, Cd(OH)₂, Co(OH)₂ and Al(OH)₃.
 10. Theprocess according to claim 4, wherein the lithium is isolated in theform of lithium carbonate or lithium fluoride.